Hobbit brain small, but organized for complex intelligence

Evolution may have endowed a controversial species with small but humanlike brains equipped to support advanced thinking

By Bruce Bower Web edition : Friday, April 3rd, 2009 Text Size

CHICAGO --- In the strange and contentious world of fossil hobbits, a chimp-sized brain may boast humanlike powers. An analysis of the inner surface of an 18,000-year- -old skull assigned to /Homo floresiensis/ , a species also known as hobbits, indicates that this tiny individual possessed a brain blessed with souped-up intellectual capacities needed for activities such as making stone tools, says anthropologist Dean Falk of Florida State University in Tallahassee.

Even as /H. floresiensis/ evolved a relatively diminutive brain, the species underwent substantial neural reorganization that allowed its members to think much like people do, Falk contended on April 2 in a presentation at the American Association of Physical Anthropologists annual meeting. She also reported the findings in a paper published online February 28 in the /Journal of Human Evolution/.

Falk compared a cast of the cranium's inner surface, or endocast, obtained from the partial hobbit skeleton LB1 to endocasts from both modern humans and from other fossil skulls in the human evolutionary family, called hominids for short. These casts bring into relief impressions made by various anatomical landmarks on the brain's surface.

"LB1 reveals that significant cortical reorganization was sustained in ape-sized brains of at least one hominid species," Falk said.

Evidence has shown that some hominid species experienced marked increases in brain size over time, but that neural reorganization took center stage for others, including hobbits, she proposes. Currently, no one knows whether a large-bodied or small-bodied species gave rise to hobbits, whose fossils have been found on the Indonesian island of Flores.

Although small in size, LB1's endocast displays a humanlike shape, Falk asserted. An endocast from /Australopithecus africanus/, a roughly 3-million-year- -old South African hominid species, looks similar to that of LB1, Falk asserted.

Yet unlike the earlier /A. africanus/, LB1 possessed a set of brain features that other researchers have implicated in complex forms of thinking by people today, she said. These features ran from the back to the front of the brain. Traits such as expanded frontal lobes and enlarged regions devoted to integrating information from disparate areas would have supported creative and innovative thinking, in Falk's view.

No signs of disease or abnormal development appear on LB1's brain surface, she noted. Some researchers argue that the specimen came from a modern human who had some type of growth disorder.

In another meeting presentation, anthropologist William Jungers of Stony Brook Health Sciences Center in New York presented evidence that LB1 did not suffer from cretinism, a growth disorder attributed to it last year by one group of researchers who doubt the fossils represent a separate species. Low levels of thyroid production cause an array of skeletal abnormalities in cretinism, as well as dwarfism.

CT scans of LB1 show no signs of dental, skull or limb conditions associated with cretinism, Jungers said. People with cretinism generally have much larger brains than that of LB1, he added.

Hobbit-fueled controversy remains strong, though. In another meeting presentation, anthropologist Robert Eckhardt of Pennsylvania State University in University Park reported that the height range within a foraging group of people now living on the hobbits' Indonesian island overlaps with height estimates for LB1. Eckhardt and his colleagues argue that, given this similarity to people today, LB1 can't be assigned to a new species.